Photomechanical negative



June 8, 1943. 2,321,046

B. RUDNICK PHOTO-MECHANICAL NEGATIVE Original Filed May 21, 1941Patented June 8, 1943 PHOTOMECHANICAL NEGATIVE Benjamin Rudnick,Huntington, N. Y., assignor to Republic Aviation Corporation,Farmingdale. N. Y., a corporation of Delaware Original application May21, 1941, Serial No.

Divided and this application November 10, 1941, Serial No. 418,435

6 Claims.

This invention relates to the preparation of a photo-mechanical negativeto be used for the photo-mechanical reproduction of drawing sheets,mechanical layouts, templates, etc.

More particularly, the invention aims to provlde a photo-mechanicalnegative which can be used in connection with the method of reproductiondisclosed in my co-pendlng application, Serial No. 394,403, led May 21,i941, of which the present application is a division.

According to one of the preferred modes of carrying out this method, astili backing sheet or plate is coated with a. layer of luminescentmaterial having an overcoating of opaque masking material. the layers ofluminescent and masking materials constituting what, for convenience, Iterm a negative surface. The copy sheet to which the design is to betransferred is coated with a lm of light-sensitive emulsion so as toform what may be referred to as a positive surface. The drawing to bereproduced is made upon the negative surface by means of a stylus orother pointed instrument which cuts or scratches through the overcoatingoi opaque masking material and uncovers the luminescent material. Afterpresenting the negative surface to a bright light, either natural orartificial, to excite the uncovered luminescent material, the treatedsurfaces are superimposed to allow the light rays emitted by theuncovered luminescent material to act upon the light-sensitive illm.Finally the copy sheet is developed and fixed in the usual photographicsolutions to reduce the exposed arcas to visible metallic silver,leaving these areas black and clear-cut, and corresponding exactly tothe lines of the original drawing.

The use of this negative is not limited to this method o! reproductiono! drawings upon sheet material, and will indeed ilnd greatly utility inmachine and sheet metal shop practice in transterring mechanical layoutsor templates as they come from the drafting table directly onto the workto be machined, metalsmithed or otherwise operated upon.

Another object of .the invention is to provide a photo-mechanicalnegative on which any kind oi line drawings may be readily marked.corrected or completed by means oi a stylus so as to form a masterpattern which may be repeatedly used for the preparation oi new drawingsor the localized correction of old drawings.

Other objects and advantages will be apparent from the followingdetailed description et two preferred modes of realisation ot myinvention,

reference being had to the annexed drawing in which:

Figures l to 4 refer to the first mode;

Figure l is a plan view of a negative or pattern sheet having a drawinginscribed thereon;

Figure 2 is a cross-sectional view of the pattem sheet taken on the line2--2 of Figure 1. the coating layers being shown, for greater`clearness, somewhat exaggerated in thickness;

Figure 3 is a cross-sectional view of a copy sheet, which is preferablyused in combination with this negative according to the method ofreproduction disclosed in the above-mentioned co-pending application,and

Figure 4 indicates the manner in which the negative and this copy sheetare arranged during their exposure.

Figures 5 and 6 are views similar to Figures 2 and 4 respectively oi'the second mode; and

Figure 7 shows a different manner in which the negative and the copysheet may be arranged during their exposure.

In Figures 1 and 2 of the drawing is illustrated a. photo-mechanicalnegative or .pattern sheet A comprising a backing sheet I, which may becomposed of paper, cardboard. metal, or any other suitable material. Onesurface of the backing sheet is thoroughly cleaned to free it from dirt,grease, or oil, following which a thin coating of white paint 2,containing no lead compounds, is applied over the surface. Upon thecoating of white paint is deposited, either by a spray or a brush, alayer of a luminescent composition 3 suspended in a transparent vehicle.For this luminescent composition I prefer to use the reaction productresulting from igniting a mixture of calcium carbonate and sulphurtogether with small quantities of bismuth or manganese salts, thisreaction product being suspended in a vehicle of unpigmentednitrocellulose lacquer thinned to a suitable consistency.

After allowing the luminescent composition to dry so that it is nolonger tacky but ilrm and hard. a thin coating of opaque maskingmaterial l is evenly distributed over its surface, so as to completelycover the luminescent layer. This masking material may comprise a blacklacquer, such as is compatible with the lacquer vehicle containing theluminescent composition.

The layer of luminescent material overlain by the coating of maskingmaterial constitutes a negative surface upon which, after drying, adrawing 5 may be inscribed by means of a stylus or other pointedinstrument, which cuts through the overcoating o! masking material andbares the luminescent composition underneath. Because of the fact thatthe masking material adheres as an extremely thin coating to theluminescent composition, it may be readily penetrated by the usualdrafting instruments, such as a pen or compass. provided with a styluspoint, and calls for no materially different technique on the part ofthe draftsman from what is lnvolved in the preparation of the usualmechanical drawings. Since the translucent nitrocellulose vehiclecarrying the luminescent composition is superimposed upon the whiteundercoating of paint 2, the lines produced by the stylus stand outsharply and clean-cut against the black background of the maskingmaterial. Should the draftsman make a mistake in initially laying outthe drawing, this may be readily corrected by painting over, and thusblacking out the incorrectiy placed lines with a black lacquercorresponding in composition to that of the masking material, thecorrect lines afterwards being added when the lacquer has dried.

The thus-prepared sheet is now placed in a strong light, which may beeither natural sunlight or artificial light, for example, ultra-violetlight, the purpose of which is to excite the luminescent compositionuncovered by the stylus so that it gives oil' radiations in a dark room.Only a few minutes is required for such excitation, following which thepattern sheet is ready for use as a master negative from whichreproductions of the drawing may be photographically transferred to copysheets, one oi such copy sheets, designated B, being shown incross-section in Figure 3.

The copy sheet B comprises a backing sheet B of metal, fabric, paper,glass, synthetic plastic, wood. or any other suitable material, or itmay constitute the actual work to be operated upon. One face of thebacking sheet is cleaned. A coating of priming material 1 is thenpainted or sprayed over the cleaned surface, the primer serving both asa filler for closing the pores of the material composing the backingsheet, and as a protective shield between the backing sheet and theemulsion which is subsequently applied thereto, and which otherwisemight interact chemically with the backing material. I prefer to use asthe primer a suspension of zinc chromate in a carrier selected withconsideration to the nature of the material composing the backing sheet.When the backing sheet is composed of a metal such as steel, both oi itsfaces, as well as its edges, will be covered with the primer to avoidcontamination of the chemicals employed in the subsequent developingoperation.

The copy sheet is next placed in a dark room illuminated, for example,by a ruby safelight of the type well known to photography; thetemperature is maintained substantially constant and an emulsion l,consisting, for example, of a light-sensitive material, such as silvernitrate suspended in a gelatinous vehicle, ismelted and applied as afilm in any suitable manner giving an even thickness, though I prefer toapply it with a low-pressure spray gun smoothly and uniformly over theprimer coating. The thus-prepared sheet is then passed through achilling chamber causing the emulsion to Jell, after which it is placedin a dryer.

The prepared copy sheet B may be used as soon as it is dry, or it may bestored away in a lighttight cabinet for future use. In transferring thedrawing from the negatively prepared surface of pattern sheet A to thepositively prepared surface of the copy sheet B. the pattern sheet isplaced upon a flat, solid support .in a dark room. treated face up, andthe copy sheet is superimposed upon the pattern sheet with its treatedface held firmly in engagement with the treated face of the patternsheet to insure absolute contact therebetween. Under such conditions,the light rays emitted by the uncovered luminescent composition actphotographically upon the lightsensitive emulsion and cause the silversalts to be sufficiently affected usually in about one and onehalf totwo minutes. The thus-exposed copy sheet is finally removed and treatedwith the usual developing and fixing solutionsin a manner which iswell-known to the photographic art, and then washed and dried, Becausenegativve surface retains its luminescence fori@ considerable time, agreat number of copiesof the drawing may be reproduced therefrom'in asingle dark room operation; and when its luminosity becomes spent it canbe restored by again presenting it to a strong light.

The drawing reproduced upon the copy sheet exhibits black,sharply-defined lines against the olive-green background of the primercoating, which is pleasing and restful to the eyes. If desired, however,the olive-green color may be bleached out to reveal the color of thebacking sheet B, by immersing the copy sheet in a dilute solution ofammonium hydroxide; or the copy sheet may be rendered transparent ifglass or a transparent plastic is employed as the backing material.

If an aluminum alloy is used as the backing of the copy sheet, thelight-sensitive emulsion can be applied directly on the metal by firstcleaning the surface in a sodium hydroxide solution and then dipping ina diluted nitric acid bath tip neutralize the caustic action. I

The negative A is particularly useful for making templates. The drawing6 indicated in Figure 1 represents a cross-section contour of anaircraft wing panel. By transferring this drawing to a sheet of metal orother rigid material in the manner already described,` and then cuttingalong the lines of the reproduced drawing. a template corresponding tothe contour of the original drawing is obtained.

Manifestly, the negative described above is'susceptible of modication.While I have found that a luminescent composition incorporating thereaction product of burned calcium carbonate and sulphur, asabove-described, gives excellent resuits besides being comparativelyinexpensive to produce, nevertheless other compositions may beadvantageously employed such, for example, as the phosphorus compounds.The coating of white paint 2 upon the pattern sheet may be omitted lfdesired, and the luminescent material applied directly to the backingsheet i. However, the presence of this white substratum advantageouslyaffects the results obtained, `particularly in those cases where thelayers of luminescent materia] is relatively thin, or where thecharacter of the backing material is such as to absorb rather than toreflect transmitted light.

The pattern sheet may be repeatedly used for the preparation of new orcorrected drawings simply bv completely or partisliymiackmg over itsinscribed surface with a fresh coating of black lacquer. After thelacquer has dried. a new and different drawing, or a localizedcorrection oi' an old drawing. may be incribed upon the renewed surface,the procedure being otherwise the same as that described above.

Another mode of preparing a negative C which can be used to reproduceonto the same lightsensitive coated copy sheets as are used in theluminous mode may be carried out in the following manner (Figures to 7)a clear plastic sheet .0i to .015 thick is coated with an opaque maskingmaterial consisting of two separate layers Ill. Ii of a metalliclacquer. These layers of me- K tallic lacquer are so applied that theycan be scribed oi or cut away, without scratching or cutting into theplastic backing sheet 9. The first coating ID is prepared by mixing aquantity of iinely ground aluminum powder in nitro-cellulose lacquer toform a thick paste. This is thinned with a mixture of solvents to asuitable consistency and is applied to the surface of the plastic sheet9. This coating I 0, when dry, renders the plastic material 9 opaque butcan readily be removed with a few strokes of a stid' brush. The materialfor the second coating Il is pre` pared by mixing a quantity of metallicpowder, which consists mainly of tin, to a greater amount ofnitro-cellulose lacquer than was used in the first coating l0. To thisis added enough solvents to thin to the desired consistency and this isapplied over the iirst layer Ill. Upon drying, the second coating Ilacts as a binder for the first coating III, The drawing to be reproduced(not shown) is drawn on this surface by means oi' a pointed instrumentwhich cuts or removes the top layer I I of masking material making itpossible to brush out the aluminum powder l0 underneath, covering thetransparent plastic backing 9. This is now used as a photographicnegative C. It is, for instance, placed in contact with thelight-sensitive copy sheet 6, l, 8 and exposed to articial light for apredetermined time. These light rays pass through the transparentportions of the plastic negative C, reacting on the light-sensitivesalts of the copy sheet B. The exposed copy sheet B is then processed inthe usual photographic solutions. The resulting reproduction appears asa sharply deiined black line on a clean contrasting background.

An outstanding advantage in the use of the plastic negative is the factthat either a right hand or left hand reproduction can be obtainedaccurately by merely placing the coated surface or the plastic negativeC (to produce a copy in reverse ot the design as drawn) in directcontact with the light-sensitive copy Plate B (as shown in Figure 6) orby placing the back or uncoated surface ot the plastic negative incontact with the light-sensitive copy plate (as shown in Figure 7).

Manii'estly, various other modifications in the foregoing modes ofpreparing the photo-mechanical negative object ot the present inventionmay be made by those skilled in the art without departing from thespirit oi my invention as deilned in the following claims.

I claim:

l. Photo-mechanical negative for reproducing designs comprising abacking member, a layer of a luminescent composition supported upon saidbacking member, and a coating of an opaque masking material overlyingsaid layer of luminescent composition, said masking material being of athickness and composition such as to be readily penetrabie by a stylus.

2. Photo-mechanical negative, for reproducing designs comprising abacking member, a layer of a luminescent composition supported upon saidbacking member comprising the reaction product resulting from burning amixture of calcium carbonate and sulphur suspended in a resinousvehicle, and a coating oi an opaque masking material overlying saidlayer of luminescent composition, said masking material being oi athickness and composition such as to be readily penetrable by a stylus.

3. Photo-mechanical negative for reproducing designs comprising abacking member, a layer of a luminescent composition supported upon saidbacking member comprising the reaction product resulting from burning amixture of calcium carbonate and sulphur together with a relativelysmall amount of a bismuth salt suspended in a resinous vehicle, and acoating of an opaque masking material overlying said layer oiluminescent composition, said masking material being of a thickness andcomposition such as to be readily penetrabie by a stylus.

4. Photo-mechanical negative for reproducing designs comprising abacking member, a layer oi a luminescent composition supported upon saidbacking member comprising the reaction product resulting from burning a.mixture of calcium` carbonate and sulphur together with a vrelativelysmall amount of a manganese salt suspended in a resinous vehicle, and acoating of an opaque masking material overlying said layer ofluminescent composition, said masking material being of a thickness andcomposition such as to be readily penetrabie by a stylus.

5. Photo-mechanical negative for reproducing designs comprising abacking member, a layer of a 'luminescent composition supported uponsaid backing member comprising the reaction product resulting fromburning a 'mixture oi' calcium carbonate and sulphur suspended in anitrocellulose lacquer vehicle, and a coating of black lacquer overlyingsaid layer ot luminescent composition, said black lacquer being of athickness such as to be readily penetrabie by a stylus.

6. Photo-mechanical negative for reproducing designs, comprising abacking sheet one of which is thoroughly cleaned, a thin coating ofwhite paint applied upon this cleaned face, a layer oi a luminescentcomposition suspended in a transparent vehicle spread and dried uponthis coating oi white paint and a thin coating oi an opaque maskingmaterial evenly distributed over the surface oi' this layer. ofluminescent compositicn.

BENJAMIN RUDNICK.

